1. Field of the Invention
The present invention relates generally to power line phase couplers and more specifically it relates to a power line phase coupler system for repeating data signals between power line phases that can be easily installed by a user.
Power line communication (PLC) is utilized to connect various electronic devices within a building structure via the electrical power system of the building. Networking of these electronic device may utilize two different but complementary PLC technologies: one for high speed data communication (computer networking, printer sharing, Internet connection, etc.) and one for control applications (designed for the lowest possible cost). Data communication applications have requirements that are completely different from control applications. Regardless of the PLC technology utilized, a home utilizing a multi-phase power line system creates several communication problems for the devices connected to the separate power line phases.
2. Description of the Prior Art
Electronic devices are commonly utilized in residential and commercial buildings to transmit data signals along the power lines of the building (i.e. power line communications). Most conventional electronic devices are electrically coupled to a single phase of the power lines of the building by simply inserting the male plug of the device into a female receptacle of a wall socket. The data signals are relatively low power signals are transmitted by a transmitter device and received by a receiver device positioned upon the same power line phase to accomplish various tasks such as turning on an appliance or adjusting the temperature within the building. The data signals are typically transmitted at relatively high frequencies typically greater than 1 KHz to reduce interference with the power line frequency of 60 Hz in North America (or 50 Hz elsewhere). LEVITON is one company that manufactures a variety of electronic devices that communicate via a building's power line system (http://www.leviton.com). There are various other manufacturers of power line communication devices such as ACT, Interactive Technologies, Inc. (ITI), Home Automation, Inc. (HAI), and X-10 PRO.
The most commonly utilized power line system within residential buildings in North America is 60 Hz, 120/240-volt split-single phase power. This power line system is basically comprised of two “phases” of power provided by three wires represented by (1) Phase A, (2) Phase B, and (3) Neutral. Phase A and Phase B of the power line system are approximately 180 degrees out of phase with respect to one another. Each of the phases carries approximately 110 to 120 volts of alternating current with respect to the neutral line. Since the phases are 180 degrees out of phase with one another the total voltage between the two phases is 240 volts. U.S. Pat. Nos. 5,192,231 and 5,187,865 provide an overview of conventional power line systems.
Since most wall outlets within building structures are “single phase” outlets (i.e. electrically connected to only one phase and ground), the data signal transmitted by the transmitter device is only transmitted along the power line phase electrically coupled to and not the other power line phase. “Natural” coupling for the data signal sometimes occur by passing passively through a phase-to-phase load (e.g. electric 240 volt water heater or stove) or through a transformer. However, consistent and reliable natural coupling is difficult to achieve and typically is not feasible for a reliable system to be implemented. Natural coupling is especially difficult to achieve in larger buildings that have numerous electronic devices connected to power outlets within the building.
To provide adequate communications for the data signal between the two phases of the building, it is often times desirable to “couple” the phases together at the breaker panel. The two most commonly utilized systems of coupling the two phases within a building structure are comprised of (1) passive couplers and (2) repeater couplers.
“Passive” couplers are typically comprised of a capacitor electrically coupled between the two phases at the breaker panel. Passive couplers do not enhance the data signal during bridging between the phases and many times a passive coupler will actually reduce the signal strength of the data signal. Utilizing a passive coupler can be difficult since the capacitor may allow the lower power frequencies and other data signals to undesirably pass between the phases. In addition, coupling the phases together at the breaker panel with a passive coupler can be difficult and dangerous even for skilled professionals. Also, the signal strength of the data signal is weakened after passing through a passive coupler and sometimes cannot be detected by a receiver device. In larger building structures a passive coupler simply is not acceptable to maintain the desirable signal strength of the receiver devices. U.S. Pat. Nos. 5,192,231 and 5,187,865 illustrate utilizing a passive coupler system that engages a wall outlet utilizing a capacitor for coupling the two phases but has the same problems as breaker panel passive couplers.
The most reliable type of power line coupler utilized today are “repeater couplers” which are electrically connected between the two phases at the breaker panel. Repeater couplers detect a data signal upon one of the phases. The repeater then amplifies and repeats the detected data signal to the second phase of the power line system. The repeated data signal is “tagged” with an identifier to prevent repeating of the already repeated data signal if received by the repeater coupler again. The LEVITON 6201 system coupler repeater is an exemplary example of a repeater coupler and is incorporated by reference into this application for the purpose of disclosing a suitable repeater coupler. The LEVITON 6201 takes data signals generated on the 120-volt line phase from which the LEVITON 6201 draws power, then boosts the data signals at the zero crossing on the other line phase of a 120/240-volt or any phase of a three-phase 120/208-volt residential wiring network. The LEVITON 6201 is typically installed at the main breaker panel, on its own dedicated 15 amp breaker (per National Electrical Code).
While these devices may be suitable for the particular purpose to which they address, they are not as suitable for repeating data signals between power line phases that can be easily installed by a user. The main problem with passive couplers is that they are not suitable for usage within larger building structures or where numerous electrical devices are connected within. The main problem with conventional repeater couplers is that they are designed to be utilized only within a main breaker panel and are not easy to utilize for most consumers.
In these respects, the power line phase coupler system according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in so doing provides an apparatus primarily developed for the purpose of repeating data signals between power line phases that can be easily installed by a user.